1. Field of the Invention
The present invention relates to an air impact driver, particularly to an air impact driver using sheet-connected screws, which a number of screws are connected in parallel.
2. Description of the Related Art
With regard to an air impact driver with compressed air as a power source, there is known an air impact driver using sheet-connected screws, which a number of screws are connected in parallel. According to an air impact driver of this kind, a slide nose is mounted to a front end portion of a main body mounted with a driver bit driven to is rotate by an air motor and the slide nose is attached with a screw feed guide and a screw feed mechanism.
The slide nose is projected forward from the main body by a compression spring and is provided with a slide stroke equal to or longer than a length of a screw. When a front end of the slide nose is pressed against the surface of a plate member or the like and the air impact driver is triggered, the driver bit rotates a screw in the slide nose, the screw is fastened by pressing the air impact driver against the plate member, the slide nose is slid by being pressed to a side of the main body of the air impact driver and the main body gets proximate to the surface of the plate member. After finishing to fasten the screw, when the air impact driver is pulled up, the slide nose returns to an initial position and a successive screw is fed into the slide nose by the screw feed mechanism.
Further, there has already been known a screw fastener for transmitting rotational torque of an air motor to a driver bit via a reduction gear and moving the driver bit in a screw fastening direction by a piston mechanism.
According to the conventional air impact driver for connecting screws, the front end portion of the main body is provided with the slide nose having the long slide stroke and in screw fastening operation, the main body of the air impact driver must be pushed to move in the direction of a screw fastening object against spring force of the compression spring mounted to the slide nose. Therefore, it is laborious.
Further, according to the mechanism for transmitting the rotational torque of the air motor to the driver bit via the reduction gear and moving the driver bit in the screw fastening direction by the piston mechanism, rotational torque of the reduction gear is continuously transmitted to the driver bit via a spline mechanism and therefore, sliding resistance at the spline mechanism portion is increased, a large piston diameter is needed for sufficiently sliding to move the driver bit and there poses a problem that large-sized tool results and repulsive force against the tool is increased.
Still further, according to the conventional air impact driver for connected screws, there is constructed a constitution in which the slide nose having the long slide stroke is provided at the front end portion of the main body and the screw is fastened by pressing the slide nose to the screw fastening object and therefore, there poses a problem that a total length of the air impact driver is long and the air impact driver is large-sized and difficult to handle.
Accordingly, there poses a technical problem to be resolved for alleviating laboriousness of screw fastening operation and it is a first object of the invention to resolve this problem.
Further, there poses another technical problem to be resolved in order to provide an air impact driver which is further small-sized and having excellent operability and it is a second object of the invention to resolve this problem.
A first aspect of the invention is proposed in order to achieve the above-described objects and provides an air impact driver for driving to rotate a driver bit by transmitting a rotational torque of an air motor to the driver bit via a centrifugal mesh clutch mechanism. The centrifugal mesh clutch mechanism, an air cylinder, and a fixed nose constituting a screw guide are arranged in one row on a same axis line. The driver bit is mounted to a front face of a piston of the air cylinder, and a spline shaft is mounted to a rear face thereof. A shaft hole slidingly paired with the spline shaft is provided at a center of a driven rotational member intermittently rotated by the centrifugal mesh clutch mechanism and fitted with the spline shaft. The spline shaft, the piston, and the driver bit advance while being rotated integrally by driving the air motor and the air cylinder to thereby fasten a screw.
A second aspect of the invention is proposed in order to achieve the above-described objects and provides an air impact driver for driving to rotate a driver bit by transmitting a rotational torque of an air motor to the driver bit via a centrifugal mesh clutch mechanism. An air motor, the centrifugal mesh clutch mechanism, an air cylinder and a fixed nose constituting a screw guide are arranged in one row on a same axis line. A driver bit is mounted to a front face of a piston of the air cylinder, and a spline shaft is mounted to a rear face thereof. A shaft hole slidingly paired with the spline shaft is provided at a center of a driven rotational member of the centrifugal mesh clutch mechanism. A hole having a diameter larger than a diameter of the spline shaft is provided at a center of a rotor of the air motor. The spline shaft of the air cylinder penetrates a shaft hole of the driven rotating member and is formed to be capable of advancing into the center hole of the rotor. The piston and the driver bit advance while rotating integrally to thereby fasten a screw by driving the air motor and the air cylinder.
A third aspect of the invention is proposed in order to achieve the above-described objects and provides an air impact driver for driving to rotate a driver bit by transmitting a rotational torque of an air motor to the driver bit via a centrifugal mesh clutch mechanism. The centrifugal mesh clutch mechanism, an air cylinder, and a fixed nose constituting a screw guide are arranged in one row on a same axis line. A driver bit is mounted to a front face of a piston of the air cylinder, and a spline shaft is mounted to a rear face thereof. A shaft hole slidingly paired with the spline shaft is provided at a center of a driven rotational member of the centrifugal mesh clutch mechanism and fitted with the spline shaft. The spline shaft, the piston, and the driver bit advance while integrally rotating to thereby fasten a screw by driving the air motor and the air cylinder. Further, a delaying circuit is inserted to an air motor control circuit to thereby delay a start timing of the air motor relative to a start timing of the air cylinder, and rotation is started after the driver bit is lowered and brought into contact with a screw head.
A fourth aspect of the invention is proposed in order to achieve the above-described objects and provides an air impact driver including an air motor, a centrifugal mesh clutch mechanism, and a double action air cylinder. A driver bit is mounted to a front face of a piston of the double action cylinder, a spline shaft is mounted to a rear face thereof. The spline shaft and a driven rotational member of the centrifugal mesh clutch mechanism are fitted to each other by a spline. A pneumatic circuit for supplying pressurized air to a retracting side air chamber of the double action air cylinder via a trigger valve at an off position of the trigger valve and for supplying the pressurized air to the air motor and an extracting side air chamber of the double action air cylinder via the trigger valve at an on position of the trigger valve. The piston, the spline shaft, and the driver bit advance while rotating integrally by making the trigger valve on, and the piston, the spline shaft, and the driver bit are retracted and returned to initial positions by making the trigger valve off.